Device for forming bumps by metal plating

ABSTRACT

Bumps are formed by means of uniform plating in which air can be easily discharged. A plating device comprises: a plating tank 32; a holding jig 34 detachably attached to an object 35 to be plated, the holding jig 34 being connected with a cathode and electrically connected with the object 35 to be plated, the object 35 to be plated being dipped in a plating solution, by the holding jig 34, substantially vertically or obliquely to the surface of the plating solution in the plating tank so that the surface to be plated can be directed upward; a cylindrical body 39 made of insulating material arranged in the front of the object 35 to be plated held by the holding jig 34 while a short clearance is left between the cylindrical body 39 and the surface to be plated and an axial line of the cylindrical body 39 is substantially perpendicular to the surface to be plated; an anode plate 37 arranged in the cylindrical body 39 being opposed to the surface of the object 35 to be plated; and a nozzle 40 arranged in the cylindrical body 39 while it penetrates the anode plate 37 and the plating solution is jetted onto the surface to be plated from the nozzle end section located in the cylindrical body 39.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of forming bumps and a devicefor metal plating.

2. Description of the Related Art

As a method of connecting semiconductor chips with a substrate, thereare known a wire bonding method, a TAB method and a flip-chip connectingmethod.

Since the flip-chip connecting method satisfies a demand for anincreased number of connecting pin points and a decreased the signalpropagation delay time, it has gradually come into wide use. Especially,because the flip-connecting method, in which solder bumps are used, iscapable of forming a large number of connections all at once, it hascome into very wide use. Examples of bump forming methods for connectingthe flip-chips are: the electrical plating method, the vapor depositionmethod, and the stud bump forming method conducted by wire bonding.

It is advantageous to use the electrical plating method because it issimple and the cost is low.

Conventionally, when bumps are formed by the electrical plating method,the following method is adopted.

First, a metallic layer made of an under-barrier-metal such as Ti/Cu,Cr/Cu and Cr/Ni is formed all over a wafer, on which wiring of a circuitused for a large number of chips has already been provided, by means ofsputtering or non-electrolytic plating.

A liquid photo-resist is coated on the metallic layer several times, sothat a resist layer, the thickness of which is approximately 50 μm, isformed. When this resist layer is processed by means ofphotolithography, fine holes are formed on the resist layer, so that aportion of the metallic layer on which bumps are formed can be exposed.

Then, solder bumps are formed on the metallic layer by the electricalplating method.

Next, the resist layer is removed and the under-barrier metal, exceptwhere the bumps are formed, is removed by means of etching.

FIG. 11 is an arrangement view showing an electrical plating devicecommonly used for the above electrical plating method.

Reference numeral 10 is an outer tank, and reference numeral 12 is a cupfacing upward. Reference numeral 14 is an anode plate horizontallyarranged in a lower portion of the cup 12. Reference numeral 16 is aplating solution jet pipe which penetrates the outer tank 10 and theanode plate 14, and an end of the plating solution jet pipe is open tothe lower portion of the cup 12. Reference numeral 18 is a holding jigcapable of holding a wafer 20 while it is electrically connected withthe wafer 20. As can be seen in the drawing, the holding jig 18 isarranged at an open portion of the cup 12 while the surface of the wafer20 to be plated is set downward. This holding jig 18 is also used as acathode.

As shown in the drawing, the plating solution is fed from the jet pipe16 into the cup 12 and further jets out toward the surface of the wafer20 to be plated. When both electrodes are energized with electriccurrent, bumps can be formed as described before.

The plating solution overflows from a gap formed between the holding jig18 and the brim of the cup 12 and drops into the outer tank 10. Afterthat, the plating solution returns to the tank via the discharge pipe22.

FIG. 12 is a view showing a profile of the bump 24 formed by the aboveelectrical plating device.

In this connection, when the bumps are formed by the above conventionalelectrical plating method, the following problems may be encountered.

In the above electrical plating device, plating is conducted as follows.An 8 inch diameter wafer, having a large number of fine holes, forexample, about 400,000 fine holes, is attached to the electrical platingdevice while the wafer is set downward, and the plating solution isjetted onto the wafer from a lower portion. Due to the abovearrangement, air tends to remain in the fine holes. As a result, thereare holes in which plating is not conducted at all or plating isconducted insufficiently. Therefore, the product yield is deteriorated.Especially, in the case of a wafer, it is sized so that it can be formedinto small narrow chips. Accordingly, the product yield of semiconductorchips is further deteriorated.

One reason for the occurrence of variation in the formation of a platinglayer is a difference in the flow rate of the plating solution betweenthe center and the periphery. Since the brim of the cup 12 is open tothe outer tank 10, the flow rate of the plating solution on theperipheral part, which overflows into the outer tank 12 of lowresistance, is higher than the flow rate of the plating solution on thecentral part. Due to the foregoing, the thickness of the plating layeron the central part tends to be larger than that on the peripheral part.

Conventionally, it is impossible to form a plating layer of largethickness because the holes are fine in the case of a wafer. In order tosolve the above conventional problem, a resist layer, the thickness ofwhich is approximately 50 μm, is formed, and the solder bump 24 isformed into a mushroom shape as shown in FIG. 12 so that a lack ofheight and quantity can be made up.

However, when the solder bump 24 is formed into a mushroom shape, thediameter of the solder bump 24 is increased. In accordance with anincrease in the diameter, it becomes difficult to form a patterndensely, which is opposite to the demand for an increased number ofpins. Further, an upper portion of the mushroom-shaped bump tends tocollapse. Therefore, it is difficult for the mushroom-shaped bumps to besubjected to the KGD (Known Good Die) electrical continuity test inwhich the bumps are pressed against the inspection wiring so as to checkthe electrical continuity.

Since the diameter of the solder bump is changed in the process ofelectric plating, that is, the diameter of the solder bump is graduallyincreased in the process of electric plating, a change is caused in thedensity of electric current. Therefore, in the case of solder plating,there is a possibility that the composition of solder is changed. Forthis reason, it is necessary to adjust the density of electric currentto be constant, which is troublesome, and further it becomes necessaryto provide an expensive device to adjust the density of electriccurrent.

SUMMARY OF THE INVENTION

The present invention has been accomplished to solve the above problems.It is an object of the present invention to provide a method of formingsolder bumps by which air can be easily discharged and uniform,excellent solder bumps can be formed. Also, it is an object of thepresent invention to provide a plating device preferably used for themethod of forming solder bumps.

In order to accomplish the above object, the present invention iscomposed as follows.

The present invention is to provide a method of forming bumps comprisingthe steps of: forming a metallic layer of under-barrier-metal on asurface of an object to be plated such as a semiconductor chip; forminga resist layer on the metallic layer; exposing a portion of the metalliclayer, in which bumps of the semiconductor chip are formed, by formingfine holes on the resist layer; dipping the object to be plated, whichis held by a holding jig, in a plating solution substantially verticallyor obliquely so that the surface of the object to be plated can bedirected upward while being opposed to an anode plate after the objectto be plated is held by the holding jig and the object is electricallyconnected with the holding jig; forming bumps in the fine holes on themetallic layer by energizing an electrode with electric current whilethe plating solution is being jetted against the surface to be platedfrom a nozzle having a nozzle section which is opposed to the surface ofthe object to be plated; removing the resist layer; and removing themetallic layer except where the bumps are formed.

According to the method described above, fine holes are directed in thelateral direction or the upward direction, and further the platingsolution is jetted out in a direction perpendicular to the surface to beplated. Therefore, air can escape smoothly from the fine holes, andplating can be effectively executed even in the fine holes. Furthermore,since the surface to be plated is dipped in the plating solution, theflow rate of the plating solution can be made substantially uniform, andit is possible to obtain a uniform plating rate. Accordingly, it ispossible to obtain a bump, the composition of which is uniform in thedirection of height.

When the solder bumps reflow by heat treatment, they are formedsubstantially spherical except for the connecting base portions of thesolder bumps.

The thickness of the resist layer and the diameter of the fine hole areadjusted so that an aspect ratio of the bump can be a value not lowerthan 0.5.

Even when the aspect ratio is not lower than 0.5, especially, even whenthe aspect ratio is not lower than 1, plating can be positivelyconducted in the fine holes because air can escape smoothly.

It is possible that the bumps to be formed are made of solder.

In this case, solder bumps composed of two layers are formed whenplating is conducted in the fine holes on the metallic layer with solderof high melting point and then plating is conducted in the fine holeswith solder of low melting point.

Due to the foregoing, the bumps are composed of the same type solderalloy. Accordingly, it is possible to form the solder bumps having ahigh adhesion property by which a fragile alloy between the solder andthe under-barrier-metal is not formed.

A cylindrical body made of insulating material is arranged on the frontside of the surface of the object to be plated while a short interval isleft between the cylindrical body and the surface to be plated, and aplating solution is jetted onto the surface of the object to be platedwhile the plating solution is shielded by the cylindrical body. Due tothe above arrangement, the flow of the plating solution can be adjustedby a clearance formed between the cylindrical body and the surface ofthe object to be plated. Accordingly, the flow rate of the platingsolution can be made uniform on the surface of the object to be plated.Therefore, it is possible to provide a uniform plating condition. As aresult, it is possible to form bumps of uniform height.

A plating device of the present invention comprises: a plating tank; aholding jig detachably attached to an object to be plated, the holdingjig being connected with a cathode and electrically connected with theobject to be plated, the object to be plated being dipped in a platingsolution, by the holding jig, substantially vertically or obliquely tothe surface of the plating solution in the plating tank so that thesurface to be plated can be directed upward; a cylindrical body made ofinsulating material arranged in the front of the object to be platedheld by the holding jig while a short clearance is left between thecylindrical body and the surface to be plated and an axial line of thecylindrical body is substantially perpendicular to the surface to beplated; an anode plate arranged in the cylindrical body being opposed tothe surface of the object to be plated; and a nozzle arranged in thecylindrical body while it penetrates the anode plate and the platingsolution is jetted onto the surface to be plated from the nozzle endsection located in the cylindrical body.

According to the device described above, it is possible to adjust theflow of the plating solution by the clearance formed between thecylindrical body and the surface of the object to be plated. Therefore,the flow rate of the plating solution can be made uniform on the surfaceto be plated. Accordingly it is possible to provide a plating layer ofuniform thickness.

It is preferable that an insulator is attached to the back of the anodeplate.

Due to the foregoing, in cooperation with the cylindrical body made ofinsulating material, it is possible to prevent the leakage of electriclines of force to the outside of the cylindrical body. Therefore, it ispossible to enhance the plating efficiency.

It is preferable that the cylindrical body is capable of moving in theaxial direction so that the distance from the cylindrical body to thesurface to be plated can be adjusted.

Due to the above arrangement, it becomes possible to adjust the platingcondition more finely.

It is preferable that a clearance is formed between the outercircumferential surface of the anode plate and the inner wall surface ofthe cylindrical body.

Due to the above arrangement, when the plating solution jets out fromthe nozzle, the plating solution flows into the cylindrical body fromthe back of the anode plate. Accordingly, the current of the platingsolution in the cylindrical body can be made smooth.

It is possible that the nozzle section is composed of a shower nozzle inwhich a large number of small holes are formed.

It is possible that a baffle plate having a large number of small holesis arranged between the surface to be plated and the nozzle section.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects of the present invention will become apparentfrom the following detailed description of the preferred embodiment ofthe invention, taken in connection with the accompanying drawings.

In the drawings:

FIG. 1 is a cross-sectional schematic illustration showing the firstembodiment of the plating device;

FIG. 2 is a cross-sectional schematic illustration showing the secondembodiment of the plating device;

FIG. 3 is a partial cross-sectional view showing a state in which ametallic layer is formed on a wafer;

FIG. 4 is a partial cross-sectional view showing a state in which a finehole is formed on a resist layer;

FIG. 5 is a partial cross-sectional view showing a state in which asolder bump is formed in a fine hole by means of plating;

FIG. 6 is a partial cross-sectional view showing a state in which aresist layer is removed;

FIG. 7 is a partial cross-sectional view showing a state in which ametallic layer is removed;

FIG. 8A is a schematic illustration showing an example of the platingprofile;

FIG. 8B is a schematic illustration showing another example of theplating profile;

FIG. 8C is a schematic illustration showing a further example of theplating profile;

FIG. 8D is a schematic illustration showing a yet further example of theplating profile;

FIG. 9 is a partial cross-sectional view of an example in which a solderbump is made of solder alloy of two layers;

FIG. 10 is a partial cross-sectional view showing a state in which asolder bump is made to reflow;

FIG. 11 is a schematic illustration of the conventional plating device;and

FIG. 12 is a schematic illustration showing an example of the profile ofthe solder bump formed by the conventional electrical plating method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the accompanying drawings, a preferred embodiment of thepresent invention will be explained in detail as follows.

First, referring to FIG. 1, the plating device 30 will be explainedbelow.

Reference numeral 32 is a plating tank, and reference numeral 33 is thelevel of the plating solution. Reference numeral 34 is a holding jig.The periphery of an object 35 to be plated, such as a wafer, is held bya holding claw 34a of this holding jig 34, so that the holding jig 34can be electrically connected with the object 35 to be plated while theobject to be plated is detachably held by the holding jig 34. Theholding jig 34 is connected to the cathode side of an electric powersource.

The object 35 to be plated is made to advance into the plating solutionperpendicularly with respect to the surface of the plating solution bythe holding jig 34. Although not shown in the drawing, the holding jig34 is supported by an appropriate supporting member. In this case, thecathode rod may be used as the support member.

It is effective to arrange the holding jig 34 in such a manner that theholding jig 34 can oscillate in the vertical direction with respect tothe plating solution and/or the transverse direction (the directionperpendicular to the surface of the drawing) due to an oscillatingmechanism not shown in the drawing. For example, the above mechanism maybe composed in such a manner that the cathode rod itself supporting theholding jig 34 is oscillated on the perpendicular surface by anappropriate crank mechanism.

Next, reference numeral 37 is an anode plate, which is arranged oppositeto the surface of the object 35 to be plated located in the platingsolution, and this anode plate 37 is supported by an appropriatesupporting member.

Reference numeral 38 is an insulating body made of a plastic which isfixed onto the back of the anode plate 37.

Reference numeral 39 is a cylindrical body made of an insulatingmaterial such as a plastic. This cylindrical body 39 is arranged in theplating solution on the front side of the surface of the object 35 to beplated while the axis of the cylindrical body 39 is set to besubstantially perpendicular to the surface to be plated and a smallclearance is formed between the cylindrical body 39 and the surface tobe plated. It is preferable to arrange the cylindrical body 39 in such amanner that the cylindrical body 39 is capable of moving in the axialdirection so that a distance from the cylindrical body 39 to the surfaceto be plated can be adjusted.

The anode plate 37 is arranged inside the cylindrical body 39. It ispreferable that a small clearance is formed between the outercircumferential surface of the anode plate 37 and the inner wall surfaceof the cylindrical body 39.

Reference numeral 40 is a nozzle, the fore end nozzle portion of whichpenetrates the plating tank 32, the anode plate 37 and the insulatingbody 38 and faces the surface of the object to be plated.

A rear end portion of the nozzle 40 is connected to a plating solutiontank (not shown in the drawing) via an appropriate hose. Therefore, theplating solution in the plating solution tank is jetted onto the surfaceto be plated by the action of a jet pump (not shown in the drawing).

In the example shown in the drawing, the nozzle portion is composed of ashower nozzle in which a large number of small holes are formed.

Reference numeral 41 is a discharge pipe through which the platingsolution is returned from the plating tank 32 to the plating solutiontank. That is, the plating solution is circulated, and the level of theplating solution in the plating tank 32 is kept constant at all times.

Reference numeral 42 is an electric power supply used for plating.

FIG. 2 is a view showing the second embodiment. The different points ofthe second embodiment from the first embodiment are that the nozzlesection of the nozzle 40 is only formed into a trumpet-shaped blow-outport and that a baffle plate having a large number of small holes isarranged between the nozzle section and the surface of the object to beplated. Other points of the second embodiment are the same as those ofthe first embodiment.

Referring to FIGS. 3 to 7, a method of forming solder bumps on a waferby the above plating device 30 will be explained as follows.

First, a metallic layer 50 composed of a Ti-layer 48 and a Cu-layer 49,is formed on a wafer 45 by means of sputtering, wherein Ti and Cu areunder-barrier-metals. In this connection, reference numeral 46 is apassivation layer, and reference numeral 47 is an aluminum wiring whichis a pad portion of the electrode shown in FIG. 3.

The metallic layer 50 may be a Cr-layer/Cu-layer or alternatively aCr-layer/Ni-layer. Further, the uppermost layer may be an Au-layer oralternatively the uppermost layer may be a layer of another metal.

Next, as shown in FIG. 4, a photo-resist layer 51 composed of dry filmis formed on the metallic layer 50, and fine holes 52 are formed bymeans of photolithography in a portion where solder bumps are formed, sothat the metallic layer 50 can be exposed. In this example, thethickness of the photo-resist layer 51 was determined to beapproximately 100 μm, however, it should be noted that the thickness isnot limited to the specific value. In this example, the diameter of thefine hole 52 was determined to be approximately 100 μm. The thickness ofthe resist layer and the diameter of the fine hole are adjusted so thatthe aspect ratio (height/diameter) of a bump to be formed can be a valuenot lower than 0.5. Since air can escape smoothly even if the aspectratio of the bump is not lower than 0.5 or especially even if the aspectratio of the bump is not lower than 1, plating can be positively carriedout in the fine holes.

In this case, a normal resist-layer may be formed instead of thephoto-resist layer. In this case, the fine holes can be formed by laserbeams generated by a excimer laser.

Reference numeral 53 is a barrier metal layer. Since the thickness of ametallic layer 50 formed by means of sputtering is too small, a barriermetal layer made of Cu or Ni is formed on the metallic layer 50 by meansof electrical plating.

Next, solder alloy plating is conducted on the metallic layer 50 in thefine holes 52 by the electrical plating device described before, so thatthe thickness of the plated metallic layer can be increased. The fineholes 52 are filled with the plated layer, that is, the plated metalliclayer is formed into a column-shape. In this way, the solder bump 54,the thickness of which is approximately 100 μm, can be formed as shownin FIG. 5. The capacity of the column-shaped solder bump, the height ofwhich is approximately 100 μm and the diameter of which is approximately100 μm, is sufficient in the case of flip-chip connection.

Next, the resist layer 51 is removed by means of etching, and themetallic layer 50, except for where the solder bumps 54 are formed, isremoved by means of etching as shown in FIG. 6.

Next, when heat treatment is conducted so that the metallic layer canreflow, it is possible to form spherical bumps 54 as shown in FIG. 7.

When the electrical plating device shown in FIG. 1 was used, the wafer,which was an object 35 to be plated, was directed in the perpendiculardirection, so that the fine holes 52 were directed in the lateraldirection and further the plating solution was jetted out from thenozzle 40 in the lateral direction. Due to the foregoing, air wassmoothly discharged from the fine holes 52 and no air remained in thefine holes 52. Therefore, it was possible to positively conduct platingin each fine hole 52.

Since the overall surface to be plated on the wafer was dipped in theplating solution, after the plating solution had been jetted out fromthe nozzle, it flowed into the outside plating solution from a clearanceformed between the periphery of the surface to be plated and the endsurface of the cylindrical body 39. When the plating solution flowed outinto the outside plating solution in this way, the flowing resistancewas so high that the flow rate was lower than the flow rate of theconventional device shown in FIG. 11 in which the plating solutionflowed into air in the outer tank 10. Accordingly, there was no bigdifference between the flow rate at the center of the surface to beplated and the flow rate at the periphery. Due to the foregoing, theplating rate in each fine hole 52 was substantially the same. Therefore,the thickness (height) of each solder bump 54 was made uniform.

As described above, even in the case of a fine hole, the depth of whichwas approximately 100 μm and the diameter of which was approximately 100μm, no defective plating was conducted, and it was possible to obtainthe solder bump 54 of uniform height.

The adhesion property of the thus obtained solder bump 54 was excellent.Further, the solder bump was formed into a column-shape of the samediameter. Therefore, the density of electric current was substantiallythe same, and the composition of solder was uniform with respect to thedirection of height.

Since it was possible to form a column-shape solder bump 54 of uniformheight, the KGD inspection was easily and positively conducted in whichthe bumps were pressed against the wiring pattern for inspection so asconduct an electrical continuity test.

In this connection, since the flow of the plating solution is adjustedby the clearance formed between the surface to be plated and the endsurface of the cylindrical body 39, a turbulent flow of the platingsolution is formed all over the surface to be plated by the flowresistance. Due to the foregoing, the plating solution comes completelyinto contact with the surface to be plated, which is one of the reasonswhy the precipitation rate of plating is uniform. The above clearance ischanged in accordance with the size of the object to be plated. Thisadjustment is conducted when the cylindrical body 39 is appropriatelymoved in the axial direction.

The clearance between the outer circumferential surface of the anodeplate 37 and the inner wall surface of the cylindrical body 39 is notnecessarily formed. However, when this clearance is provided, theplating solution flows from the rear side of the anode plate 37 into thecylindrical body 39 in accordance with the flow of the plating solutionjetted out from the nozzle 40. Due to the foregoing, the platingsolution flows smoothly in the cylindrical body 39.

When the cylindrical body 39 is made of insulating material and theinsulating member 38 is fixed onto the back of the anode plate 37, itbecomes possible to prevent the electric lines of force from leakingoutside the cylindrical body 39. Accordingly, it is possible to enhancethe plating efficiency.

In this connection, when the object to be plated is changed, forexample, when the object to be plated is changed from an 8 inch wafer toa 4 inch wafer, the cylindrical body 39 may be replaced with anotherone, the diameter of which corresponds to the size of the wafer. Whenthe cylindrical body 39 is replaced, it is moved to the front of theanode plate 37. In this way, the cylindrical body 39 can be easilydisconnected from the plating tank 32 and replaced with another one.

The cylindrical body 39 may not be necessarily arranged depending uponthe type of the object to be plated.

Table 1 shows ratios of the shape of plating in the case where theplating device shown in FIG. 1 or 2 was used and also in the case wherethe conventional plating device shown in FIG. 11 was used.

                  TABLE 1                                                         ______________________________________                                        Ratios (%) of the shape of plating in each mode                                                    Device shown in                                                   Conventional Device                                                                       FIG. 1                                                   ______________________________________                                        Mode A     8.3           0                                                    Mode B     35.9          0                                                    Mode C     56.8          100                                                  Mode D     0             0                                                    ______________________________________                                    

When the conventional plating device was used, the defect of Mode A, inwhich the plated layer was not attached onto the wafer as shown in FIG.8A, was 8.3%, and the defect of Mode B (FIG. 8B), in which the defectoccurred when the plating solution flowed in parallel with the wafer,was approximately 40%.

On the other hand, when the plating device shown in FIG. 1 was used,since the fine holes were arranged in the lateral direction and theplating solution was jetted out onto the surface to be plated in thelateral direction, air easily escaped. Accordingly, no defect was causedin Mode A, Mode B and Mode D (FIG. 8D), and the percentage of good bumpswas 100%. In this experiment, plating was conducted aiming at Mode C(FIG. 8C).

FIGS. 9 and 10 are views respectively showing an example in which thesolder bump 54 is composed of two layers of solder.

That is, the lower layer (the layer on the metallic layer 50 side) iscomposed of a high melting point solder section 54a, the melting pointof which is high because the tin content is low, and the upper layer iscomposed of a low melting point solder section 54b, the melting point ofwhich is low because the tin content is high.

In order to form the two layers described above, first, the high meltingpoint solder section 54a is formed in a plating bath of high meltingpoint solder, and then the plating tank is changed, and the low meltingpoint solder section 54b is formed in a plating bath of low meltingpoint solder.

When the low melting point solder section 54b is made to reflow, it ispossible to form a substantially spherical solder bump 54 as shown inFIG. 10.

When the bump 54 is made of the high melting point solder section 54a,which is a core of the bump, since the bump is made of the same typemetal (solder alloy), the high melting point solder section and the lowmelting point solder section adhere to each other tightly and themechanical strength is high, and further since the core is provided inthe bump, it can not be damaged in the process of mounting.

Since the core is composed of the high melting point solder section 54a,the tin content of which is low, even if the under-barrier-metal iscopper, there is no possibility of the formation of tin-copper alloywhich is fragile. Accordingly, the solder adheres to the under-layerstrongly, and the copper layer is not damaged. Therefore, the aluminumwiring can be sufficiently protected.

In the plating device 30 shown in FIG. 1 or 2, the object to be platedis held by the holding jig 34 and dipped in the plating solution whileit is held perpendicularly to the surface of the plating solution.However, the object to be plated may be dipped in the plating solutionwhile it is held obliquely to the surface of the plating solution sothat the plating surface can be directed upward (not shown in thedrawing). In accordance with the above oblique arrangement of the objectto be plated, the cylindrical body 39 and the nozzle 40 are alsoarranged obliquely.

In this case, since the fine holes on the wafer are directed upward, aircan escape from the fine holes more easily although it becomes difficultto set the holding jig 34 in the plating solution and also it becomesdifficult to pick up the holding jig 34 from the plating solution.

In the above embodiments, the bumps are made of solder alloy, however,it is possible to apply the present invention to the bumps made of othermetals such as nickel and gold. The lower layer of the bump may be madeof nickel, and the upper layer of the bump may be made of gold, that is,the lower and the upper layer may be made of the same or the differenttype metals, the number of which is not less than two.

It is preferable to apply the above plating device 30 to the formationof solder bumps used for a micro BGA package or a wafer. Especially, itis preferable to apply the above plating device 30 to the formation ofsolder bumps used for a wafer. Of course, the above plating device 30can be put into common use. Even in this case, it is possible to form auniform plated layer on an inner wall in a small space.

According to the invention, the fine holes are directed in the lateraldirection or the upward direction, and further the plating solution isjetted out in the perpendicular direction to the surface of an object tobe plated. Therefore, air can easily escape from the fine holes, and itbecomes possible to conduct plating even in the fine holes. Further,since the surface of the object to be plated is dipped in the platingsolution, the flow rate of the plating solution jetted out from thenozzle becomes substantially uniform, and it becomes possible to obtaina uniform precipitation rate. Accordingly, it is possible to form a bumpwhich is uniform in composition in the direction of height.

It is to be understood that the invention is by no means limited to thespecific embodiments illustrated and described herein, and that variousmodifications thereto may be made which come within the scope of thepresent invention as defined in the appended claims.

We claim:
 1. A plating device comprising:a plating tank; a holding jigdetachably attached to an object to be plated, the holding jig beingconnected with a cathode and electrically connected with the object tobe plated, the object to be plated being dipped in a plating solution bythe holding jig substantially vertically or obliquely to the surface ofthe plating solution in the plating tank so that the surface to beplated can be directed upward; a cylindrical body made of an insulatingmaterial arranged in the front of the object to be plated held by theholding jig while a clearance is left between the cylindrical body andthe surface to be plated and an axial line of the cylindrical body issubstantially perpendicular to the surface to be plated; an anode platearranged in the cylindrical body being opposed to the surface of theobject to be plated; and a nozzle arranged in the cylindrical body whileit penetrates the anode plate and the plating solution is jetted ontothe surface to be plated from the nozzle end section located in thecylindrical body.
 2. The plating device according to claim 1, wherein aninsulator is attached to the back of the anode plate.
 3. The platingdevice according to claim 1, wherein the cylindrical body is capable ofmoving in the axial direction so that a distance from the cylindricalbody to the surface to be plated can be adjusted.
 4. The plating deviceaccording to claim 1, wherein a clearance is formed between the outercircumferential surface of the anode plate and the inner wall surface ofthe cylindrical body.
 5. The plating device according to claim 1,wherein the nozzle section is composed of a shower nozzle in which alarge number of holes are formed.
 6. The plating device according toclaim 1, wherein a baffle plate having a large number of holes isarranged between the surface to be plated and the nozzle section.